Porous catalyst carrier with three-periodic minimal surface and variable porosity and its establishment method

Abstract

The present invention discloses a method for establishing a porous catalyst carrier with three-period minimal surface of variable porosity, characterized in that the method comprises the following steps: step 1. modeling of uniform porous catalyst carriers with different porosities; step 2. determining the porosity distribution scheme of the porous catalyst carrier with variable porosity by analyzing the finite element model of the flow field of the porous catalyst carrier with three-period minimal surface of uniform porosity; step 3. topological optimization is performed using the porosity characteristic parameters of the three-period minimal surface to generate a geometric file of the porous catalyst carrier with variable porosity; step 4. simulating and verifying the catalytic performance using a multi-physical field finite element analysis method: if the simulation result meets the catalytic performance requirements, proceed to step 5; if the simulation result does not meet the catalytic performance requirements, return to step 2; step 5. the geometric file of the porous catalyst carrier with variable porosity is generated using 3D printing technology to generate a solid porous catalyst carrier. The method can improve the catalytic reaction performance and obtain a catalyst carrier with a high conversion rate.

Description

Technical Field

[0001] The present invention relates to the field of catalyst materials, and in particular to a variable porosity three-periodic minimal surface porous catalyst carrier and a method for establishing the same. Background Art

[0002] Porous structure is a complex topological structure widely found in nature and industry. It has the characteristics of large specific surface area, high porosity, lightweight, and excellent mechanical properties. It is widely used in lightweight core technology fields such as aerospace, bridges, and medical implants. In recent years, porous structures have been gradually valued in the field of chemical catalysis because of their large specific surface area, large tortuosity, and other characteristics that make them particularly suitable as high-performance catalytic reaction carriers. In response to this, researchers have developed a variety of structured catalyst carriers including porous metal / non-metal foams, honeycomb structures, and lattice structures, and have successfully applied them to high-performance catalytic reaction systems such as automobile exhaust treatment, alcohol fuel reforming, and catalytic combustion, achieving good performance and economic value. For example, patent document CN 110038608 A discloses a structured catalyst material for VOCs catalytic combustion. The catalytic material uses foamed silicon carbide with a porous structure, high thermal conductivity, and high strength as a carrier, and exhibits good VOCs catalytic oxidation performance. However, due to their own discontinuity, the honeycomb and lattice structures are not fully connected internally and have strong anisotropy, which results in limited transport of reactants inside them compared to porous foam structures, which is not conducive to the full and rapid progress of the catalytic reaction.

[0003] However, most of the porous foam and porous fiber catalyst carrier synthesis methods published so far are composed of disordered unit cell structures. Not only does the unit cell structure have large anisotropy, but the overall catalyst carrier also exhibits strong anisotropy. As a result, these porous catalyst structures are prone to internal thermal stress concentration when exposed to external or internal heat sources of chemical reactions, which leads to excessive and uneven distribution of hot and cold spots inside the structure, affecting the catalytic reaction, reducing catalyst performance, and causing the loaded catalyst to sinter and fall off. Therefore, improving the continuity and controllability of the catalyst carrier structure is the focus of future research to improve the performance of structured catalyst carriers.

[0004] In recent years, with the rapid development of micro 3D printing technology, the high-precision synthesis of complex parameterized microstructures has gradually become possible. In the theory of geometric topology, Triple Periodic Minimal Surfaces (TPMS) is a smooth continuous bionic surface with a surface average curvature of zero. The generation of this surface follows the law that the synthesis of natural materials proceeds in the direction of minimum energy. Similar structures are found in many insect wings, marine organisms, leaves, etc. TPMS has natural porous continuous characteristics and can be expressed by implicit functions, thereby accurately controlling the pore size, distribution and shape, which provides an ideal solution for the parametric design of high-performance catalyst carriers. Patent document CN111737835A discloses a three-dimensional porous heat dissipation structure and optimization method based on three-periodic minimal surfaces to improve the heat dissipation performance, thermal conduction efficiency and effectiveness of the structure. However, the purpose of the above CN 111737835 A is only to enhance the heat dissipation performance and heat conduction. The application of TPMS in the design and optimization of catalytic reactions, giving full play to the advantages of TPMS such as smooth and continuous structure, high controllable precision, strong thermal conductivity, and large specific surface area, to improve catalytic reaction performance is not mentioned in the prior art. Therefore, the technical problem to be solved by the present invention is how to produce a catalyst carrier with a high conversion rate based on TPMS parametric design and 3D printing technology. Summary of the invention

[0005] In order to solve the above problems in the prior art, the present invention provides a variable porosity three-period minimal surface porous catalyst carrier and an establishment method to solve the technical problem of how to improve the catalytic reaction performance and produce a catalyst carrier with a high conversion rate.

[0006] In one aspect, the present invention provides a method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier, the method comprising the following steps:

[0007] Step 1: Modeling of uniform porous catalyst supports with different porosities;

[0008] Step 2: Determine the porosity distribution scheme of the variable porosity porous catalyst carrier by analyzing the finite element model of the flow field of the uniform porosity three-period minimal surface catalyst carrier;

[0009] Step 3: Use the porosity characteristic parameters of the three-periodic minimal curve to perform topology optimization and generate a variable porosity porous catalyst support geometry file;

[0010] Step 4: Use multi-physics finite element analysis method to simulate and verify the catalytic performance:

[0011] If the simulation results meet the catalytic performance requirements, proceed to step 5;

[0012] If the simulation results do not meet the catalytic performance requirements, return to step 2

[0013] Step 5: Based on the generated variable porosity porous catalyst carrier geometry file, a solid porous catalyst carrier is generated using 3D printing technology.

[0014] The present invention is composed of a three-periodic minimal surface porous structure cell body that can be designed with a variable porosity distribution according to the carrier flow field. Due to the variable porosity distribution design of the porous carrier, the vertical mainstream disturbance of the flow field inside the uniform porous catalyst carrier and the residence time of the reactants are significantly improved. When the reactants enter the three-periodic minimal surface porous catalyst carrier with a variable porosity distribution, the overall catalytic performance can be significantly improved.

[0015] Further, an optimization scheme for the method of establishing a porous catalyst carrier with three-periodic minimal surface having variable porosity of the present invention is proposed. The modeling of the uniform porous catalyst carrier with different porosities described in step 1 comprises the following steps:

[0016] Through the unified implicit function of the three-periodic minimal surface, the isosurface function expression φ of the three-periodic minimal surface is generated. (x,y,z) =C, C is the equivalent parameter, C∈[-1,1], and the uniform porous structure model with different porosity is obtained according to different C;

[0017] The shell structure and rib column structure with a certain thickness are constructed by using the equivalent parameter C;

[0018] The equivalent function parameter C is optimized to generate a variable porosity porous catalyst support model.

[0019] The present invention utilizes the different unit cell structures of a variable porosity porous carrier on each cross section along the direction perpendicular to the main flow to enhance the degree of disturbance in the direction perpendicular to the main flow; in order to extend the overall residence time of the reactants in the carrier, the present invention draws on the principle of gradually expanding tubes in aerodynamics and adopts a strategy of gradually increasing the porosity along the mainstream direction, thereby achieving the purpose of reducing the overall flow velocity of the reactants and thereby extending the residence time.

[0020] Further, an optimization scheme for the method of establishing a porous catalyst carrier with three-periodic minimal surfaces of variable porosity of the present invention is proposed, wherein the three-periodic minimal surfaces include: G surface, IWP surface, P surface and S surface, and the mathematical expressions of the three-periodic minimal surfaces corresponding to each surface are as follows:

[0021] G surface: φ G =sinXcosY+sinYcosZ+sinZcosX=C

[0022] IWP Surface:

[0023] φ IWP=2(cosXcosY+cosYcosZ+cosZcosX)-(cos2X+cos2Y+cos2Z)=C

[0024] P surface: φ P =cosX+cosY+cosZ=C

[0025] S-surface: φ S =cos2XsinYcosZ+cosXcos2YsinZ+sinXcosYcos2Z=C

[0026] Where X=2απx, Y=2βπy, Z=2γπz, x, y, z are spatial coordinates, α, β, γ are the magnification factors of the three-periodic minimal surface at a fixed unit cell size. Different magnification factors or unit cell sizes can be used for design and optimization according to actual needs.

[0027] A preferred scheme for the method of establishing a variable porosity three-period minimal surface porous catalyst carrier of the present invention is further proposed, wherein the shell structure is generated by defining a closed area surrounded by two different equivalent minimal surfaces with the same period and frequency, and the rib column structure is generated by defining the relationship between the equivalent function of a three-dimensional space and the equivalent function value of a minimal surface.

[0028] A preferred solution of the method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier of the present invention is further proposed, wherein the porous catalytic shell structure carrier is defined by ±C: -C≤φ sheet ≤C, C≠0; define the area less than C as the solid area, and the area greater than C as the vacuum area: φ solid <C,φ volume >C, where φ sheet ,φ solid ,φ volume They represent the equivalent function values ​​corresponding to the shell structure, rib column structure and vacuum area respectively.

[0029] A preferred solution of the method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier of the present invention is further proposed, wherein step 2 comprises the following steps:

[0030] A finite element model of the flow field of a porous catalyst carrier with three-periodic minimal surfaces of uniform porosity is established; the flow distribution of reactants inside the porous catalyst carrier with three-periodic minimal surfaces of uniform porosity is calculated and analyzed to obtain the flow distribution law of reactants; and the parameterized optimization scheme of the porous catalyst carrier with variable porosity is determined based on the flow distribution law of reactants.

[0031] A preferred scheme for the method of establishing a variable porosity three-periodic minimal surface porous catalyst carrier of the present invention is further proposed, wherein the flow distribution law of the reactants includes: the distribution law in the direction parallel to the flow and the distribution law in the direction perpendicular to the flow in the catalyst carrier.

[0032] A preferred solution of the method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier of the present invention is further proposed, and the multi-physics field finite element analysis method used in step 4 is:

[0033] Based on the porosity distribution scheme of the variable porosity porous catalyst carrier described in step 2, multi-physics field finite element numerical simulation is used to apply specific boundary conditions and analyze the catalytic performance.

[0034] A preferred scheme for the porosity distribution scheme of the variable porosity porous catalyst carrier described in the present invention is further proposed, wherein the 3D printing technology includes molten deposition, selective laser sintering, selective laser melting, and stereoscopic printing; the 3D printing material is a high thermal conductivity ceramic, a silicon-based material, or a metal material, wherein the metal material includes an aluminum alloy, stainless steel, a titanium alloy or a magnesium alloy.

[0035] At the same time, the present invention provides a variable porosity three-period minimal surface porous catalyst carrier, which is obtained using the aforementioned establishment method.

[0036] The present invention has the following beneficial effects:

[0037] (1) The variable porosity three-period minimal surface porous catalyst carrier provided by the present invention is composed of a three-period minimal surface unit cell structure with a porosity gradient changing along the mainstream direction. Under the conditions where reactants flow in and participate in chemical reactions, due to the characteristics of the three-period minimal surface structure such as smoothness and continuity, strong thermal conductivity, and large specific surface area, the catalyst's surface adhesion performance is greatly improved, and the internal temperature distribution is more uniform, the number of hot and cold spots is effectively reduced, and the catalytic performance of the reaction chamber is enhanced. On the other hand, the variable porosity three-period minimal surface structure greatly promotes the disturbance of the reactants in the direction perpendicular to the mainstream, and prolongs the residence time of the reactants in the carrier, thereby promoting the overall reactant conversion efficiency.

[0038] (2) The present invention discloses a method for establishing a variable porosity three-period minimal surface porous catalyst carrier. The smoothness and precise controllability of the minimal surface structure greatly improve the designability of the catalyst carrier. According to the optimization scheme of the present invention, a variable porosity porous catalyst carrier structure that adapts to the actual flow of reactants can be extended, which has a wider applicability. Using 3D printing technology, the processing steps of the porous structure can be simplified, saving a lot of manpower and time.

[0039] (3) The present invention can select a suitable porosity and variable porosity distribution scheme according to the required reactant flow distribution and multi-physical field performance indicators. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 These are four types of three-periodic minimal surface isosurfaces used in Example 1 of the present invention, where Figure (a) is a G surface, Figure (b) is an IWP surface, Figure (c) is a P surface, and Figure (d) is an S surface.

[0041] Figure 2 The present invention is a flow chart for the design and preparation of a variable porosity three-periodic minimal surface porous catalyst carrier.

[0042] Figure 3 This is the IWP rib-type porous catalyst carrier used in Example 2 of the present invention. Figure (a) is a uniform porous catalyst carrier with a porosity of 50%, Figure (b) is a uniform porous catalyst carrier with a porosity of 80%, and Figure (c) is a gradient porous catalyst carrier with a porosity of 50% to 80%.

[0043] Figure 4 Figure 2 shows the streamline distribution results of different porous catalyst carriers in Example 2 of the present invention. Figure (a) is the flow field result of a porous catalyst carrier with uniform porosity of 50%, Figure (b) is the flow field result of a porous catalyst carrier with uniform porosity of 80%, and Figure (c) is the flow field result of a porous catalyst carrier with a porosity gradient of 50% to 80%.

[0044] Figure 5 The results of the distribution of the mass fraction of methanol reactants in different porous catalyst supports in Example 2 of the present invention are as follows: Figure (a) is the distribution of the mass fraction of methanol reactants in a porous catalyst support with a uniform porosity of 50%, Figure (b) is the distribution of the mass fraction of methanol reactants in a porous catalyst support with a uniform porosity of 80%, and Figure (c) is the distribution of the mass fraction of methanol reactants in a porous catalyst support with a gradient porosity of 50% to 80%.

[0045] Figure 6 Figure 2 is a radially variable porosity porous catalyst carrier in an embodiment of the present invention. Figure (a) is a G rib column type porous catalyst carrier, Figure (b) is an IWP rib column type porous catalyst carrier, Figure (c) is a P rib column type porous catalyst carrier, Figure (d) is a D rib column type porous catalyst carrier, and Figure (e) is an S rib column type porous catalyst carrier. DETAILED DESCRIPTION

[0046] In order to more clearly explain the purpose, technical solution and advantages of the present invention, the present invention is further described below in conjunction with specific implementation methods and drawings. It should be understood that the description is only exemplary and does not limit the scope of application of the present invention.

[0047] Example 1

[0048] See also Figure 1 and Figure 2 The present disclosure provides a method for establishing a variable porosity three-period minimal surface porous catalyst carrier, the method comprising the following steps:

[0049] Step 1: Modeling of uniform porous catalyst supports with different porosities.

[0050] Input the isosurface function expression of the three-periodic minimal surface φ (x,y,z) =C, C is an equivalent parameter. According to different C (C∈[-1,1]), porous structure models with different porosities are obtained. According to the shell structure and rib column structure definitions, uniform porous catalyst carriers with different porosities are generated. The variable porosity porous agent carrier is designed by the equivalent parameter C, which can realize single-axis linear porosity gradient, single-axis nonlinear porosity gradient, multi-axis nonlinear porosity gradient, etc.

[0051] In this embodiment, the specific operation process is:

[0052] (1) Mathematical representation of isosurfaces of three-periodic minimal surfaces

[0053] There are many types of three-periodic minimal surfaces, and their unified implicit function expressions are:

[0054]

[0055] in is a three-dimensional space point vector, is the reciprocal lattice vector, is the shifted phase within the trigonometric function, is the vector amplitude. When the above expression is truncated to a certain value, an equivalent level set function φ(x, y, z) = C composed of trigonometric functions will be approximately generated. Many minimal surface function expressions can be derived from the above implicit function. The preferred three-periodic minimal surfaces of the porous catalyst carrier of the present invention include G surface, IWP surface, P surface, and S surface.

[0056] The mathematical expressions of the three-periodic minimal surfaces of the above-mentioned priority surfaces are as follows:

[0057] G surface: φ G =sinXcosY+sinYcosZ+sinZcosX=C

[0058] IWP Surface:

[0059] φ IWP =2(cosXcosY+cosYcosZ+cosZcosX)-(cos2X+cos2Y+cos2Z)=C

[0060] P surface: φ P =cosX+cosY+cosZ=C

[0061] S-surface: φ S =cos2XsinYcosZ+cosXcos2YsinZ+sinXcosYcos2Z=C

[0062] Where X = 2απx, Y = 2βπy, Z = 2γπz, x, y, z are spatial coordinates, α, β, γ are magnification factors of the three-periodic minimal surface at a fixed unit cell size, and different magnification factors or unit cell sizes can be used for design and optimization according to actual needs. In this embodiment, the three-periodic minimal surface unit cell size of 2×2×2mm is taken as the minimum unit, and the magnification factor is taken as 0.5 as an example to design and optimize the porous catalyst carrier.

[0063] (2) Modeling of three-periodic minimal surface porous catalyst carrier

[0064] Based on the three-periodic minimal surface isosurface function established above, a shell structure and a rib column structure with a certain thickness are further constructed by using the isoparameter C. The shell structure is a thin shell structure with a certain thickness, which is generated by defining a closed area surrounded by two different isoparameter minimal surfaces with the same period and frequency. The present invention uses symmetric isoparameters ±C to define a porous catalytic shell structure carrier:

[0065] -C≤φ sheet ≤C,C≠0

[0066] The rib column structure is composed of a columnar structure with a certain thickness and shape, and is generated by defining the relationship between the equivalent function of a three-dimensional space and the equivalent function value of a minimal surface. The present invention defines the area less than C as a solid area, and the area greater than C as a vacuum area:

[0067] φ solid <C

[0068] φ volume >C

[0069] where φ sheet ,φ solid ,φ volume Represent the equivalent function values ​​corresponding to the shell structure, rib column structure and vacuum area respectively. In the above definition, the equivalent parameter C determines the thickness of the shell structure and the rib column structure, and then determines the porosity of the porous three-periodic minimal surface carrier. Therefore, the design of porous catalyst carriers with non-uniform porosity distribution can be satisfied by optimizing the equivalent function parameter C.

[0070] Step 2: Determine the porosity distribution scheme of the variable porosity porous catalyst carrier by analyzing the finite element model of the flow field of the uniform porosity three-period minimal surface catalyst carrier.

[0071] A finite element model of the flow field of a porous catalyst carrier with three-period minimal surfaces of uniform porosity is established, and the flow distribution of reactants inside the porous carrier with uniform porosity is calculated and analyzed. According to the distribution law of the flow field in the porous catalyst carrier parallel and perpendicular to the flow direction, a parametric optimization scheme of the porous catalyst carrier with variable porosity is determined. The method in this embodiment is specifically as follows: Based on the above-mentioned three-period minimal surface entity parameterization synthesis method, a porous catalyst carrier with uniform porosity is established, and specific import and export constraints are imposed. The finite element method is used to analyze the flow distribution of reactants inside the uniform porous catalyst carrier, and then the porosity distribution scheme of the porous carrier is determined.

[0072] (1) Establishment of finite element flow model of porous catalyst carrier

[0073] Based on the above purpose, the finite element flow model of the three-periodic minimal surface porous catalyst carrier is established as follows:

[0074] The governing equation for mass conservation is:

[0075]

[0076] The governing Navier-Stokes momentum conservation equations are:

[0077]

[0078] Where ρ is the reactant density, is the reactant vector flow field, p is the reactant pressure, and μ is the reactant dynamic viscosity.

[0079] Inlet boundary conditions:

[0080]

[0081] in is the velocity vector of the inlet reactant, u0 is the initial velocity, is a unit vector.

[0082] Outlet boundary conditions:

[0083] p out =1[atm]

[0084] Where P out is the outlet pressure and atm is the atmospheric environment.

[0085] (2) Optimization scheme for variable porosity distribution

[0086] In order to obtain an optimization scheme for variable porosity distribution, the above-mentioned finite element flow model needs to be analyzed. The optimization scheme for porosity distribution needs to be guided by how to increase the degree of mixing inside the catalyst carrier in the direction perpendicular to the main flow and to extend the overall residence time of the reactants in the catalyst carrier. According to flow field analysis, the internal flow field of a porous catalyst carrier with uniform porosity tends to be uniform, and the mixing disturbance in the direction perpendicular to the mainstream is relatively weak. However, the unit cell structure of the porous carrier with variable porosity is different on each cross section along the direction perpendicular to the mainstream, which strengthens the degree of disturbance in the direction perpendicular to the mainstream. In order to extend the overall residence time of the reactants in the carrier, the present invention draws on the principle of gradually expanding tubes in aerodynamics and adopts a strategy of gradually increasing porosity along the mainstream direction to achieve the purpose of reducing the overall flow velocity of the reactants and thus extending the residence time.

[0087] The variable porosity distribution of the porous catalyst carrier is realized by optimizing the equivalent parameter C of the three-periodic minimal surface. The present invention adopts two embodiments to design the variable porosity porous carrier, namely, the single-axis linear change of the equivalent parameter C and the biaxial nonlinear change of the equivalent parameter C, to achieve the purpose of increasing the porosity of the porous structure along the mainstream direction. Take the linear change of porosity along the x-axis as an example:

[0088] ε x =f(x)=a·x+ε x＝0

[0089] where ε x is the porosity of the three-periodic minimal surface unit cell at the x coordinate, a is the porosity change rate of the linear change scheme, ε x＝0 is the porosity of the unit cell of the three-periodic minimal surface at the origin of the coordinate system.

[0090] C=g(ε x )

[0091] C=h(x)

[0092] According to the fitting relationship between the equivalent parameter C of the three-periodic minimal surface and the unit cell porosity ε, the variation law of the characteristic parameter C of the variable porosity porous carrier along the x-axis is obtained, and then the variable porosity porous catalyst carrier STL geometry file can be generated on this basis. It should be noted that the variable porosity carrier generation method described in the present invention is not limited to linear changes along a single coordinate. This is only an example to illustrate the principle. This principle is also applicable to the geometric generation of complex pore gradient carriers such as single coordinate nonlinear pore gradient and multi-coordinate nonlinear.

[0093] Step 3: topology optimization is performed using the porosity characteristic parameters of the three-periodic minimal curve surface to generate a variable porosity porous catalyst carrier geometry file. The geometry file in the present invention uses an STL format file.

[0094] Specifically, the method in this embodiment is: based on the parametric optimization scheme of the variable porosity porous catalyst carrier obtained in step 2, combined with the mathematical expression of the three-periodic minimal surface, a triangular mapping mesh is generated. Specifically, the mathematical software MATLAB can be used to generate the triangular mapping mesh; illegal meshes are deleted according to the tracking algorithm, and then combined with the parameterized three-periodic minimal surface to output the STL geometry file of the variable porosity porous catalyst carrier.

[0095] Step 4: Use multi-physics finite element numerical simulation to verify the catalytic performance:

[0096] If the simulation results meet the catalytic performance requirements, the next step is to generate a solid porous catalyst carrier using 3D printing technology based on the generated variable porosity porous catalyst carrier STL geometry file.

[0097] If the simulation results do not meet the catalytic performance requirements, it is necessary to return to step 2, correct the variable porosity distribution scheme through the variable porosity distribution optimization method provided in step 2, and re-determine the variable porosity distribution scheme; then repeat steps 3 and 4 until the simulated catalytic performance meets the requirements, and then proceed to the next step 5.

[0098] The multi-physics field finite element numerical simulation method in this embodiment is specifically: based on the porosity distribution scheme of the porous catalyst carrier mentioned above, a multi-physics field finite element numerical simulation method is used to apply specific boundary conditions to analyze the catalytic performance.

[0099] At the same time, the catalytic performance analysis here can be further guided by multi-physical field information, combined with the accuracy requirements of 3D printing technology, to iteratively optimize the porosity distribution scheme and obtain a variable porosity catalytic carrier with optimal or specified catalytic performance.

[0100] Based on the above purpose, the multi-physics finite element model of variable porosity porous catalyst carrier is established as follows:

[0101] The governing equation for energy conservation is:

[0102]

[0103] Maxwell's governing equations for material diffusion:

[0104]

[0105] Among them C p is the constant pressure specific heat capacity of the reactant, T and k are the reactant temperature and the effective thermal conductivity of the reactant, respectively, Q react is the heat source of the catalytic reaction, u, v, w represent the speed in the x, y, z directions respectively, ω i is the mass fraction of substance i in the reactants, D is the multi-component Fick diffusion coefficient matrix between the reactants, Ri is the catalytic reaction rate of reactant i.

[0106] Step 5: According to the generated variable porosity porous catalyst carrier STL geometry file, a solid porous catalyst carrier is generated by 3D printing technology, that is, the variable porosity three-period minimal surface porous catalyst carrier disclosed in the present invention. The 3D printing technology in this embodiment includes molten deposition, selective laser sintering, selective laser melting, and stereoscopic printing. The 3D printing material is a high thermal conductivity ceramic, a silicon-based material, or a metal material, wherein the metal material includes an aluminum alloy, stainless steel, a titanium alloy, or a magnesium alloy.

[0107] The above-mentioned method for establishing a variable porosity three-period minimal surface porous catalyst carrier optimizes the variable porosity distribution according to the flow field information of the three-period minimal surface porous catalyst carrier, so that the obtained catalyst carrier has a more reasonable flow field distribution and high conversion efficiency, which greatly improves the catalytic reaction performance.

[0108] Example 2

[0109] like Figure 3 As shown, on the basis of Example 1, this example is based on the mathematical expression of the IWP-type three-periodic minimal surface in the present invention, and uses MATLAB mathematical software to generate a uniform porous catalyst carrier with a unit cell size of 2×2×2mm and an overall size of 2×2×8mm. By selecting different equivalent parameters C, porous catalyst carriers with porosities of 50% and 80% were determined for comparison. According to the internal flow characteristics of porous catalyst carriers with different porosities above, it can be concluded that the flow velocity of low-porosity carriers is larger, and the lateral disturbance is weaker than that of high-porosity carriers. Therefore, based on the basic principle of increasing the degree of mixing inside the catalyst carrier perpendicular to the main flow direction and prolonging the overall residence time of the reactants in the catalyst carrier, a linear gradient porous carrier with an inlet porosity of 50% and an outlet porosity of 80% was designed by adopting a strategy of gradually increasing the porosity along the mainstream direction. According to Figure 4 The analysis results show that it can be clearly seen that the flow velocity range inside the linear gradient pore carrier increases and the lateral turbulence is significantly enhanced.

[0110] This embodiment is designed with methanol steam reforming hydrogen production as the reaction system. The methanol steam reforming hydrogen production reaction equation is as follows:

[0111] SR:CH3OH+H2O→3H2+CO2

[0112]

[0113] Based on the multi-physics finite element method, the performance of porous catalyst supports under different design parameters is analyzed by coupling fluid heat transfer, fluid flow, material transfer and chemical reaction. Figure 5It can be seen that the catalytic performance of uniform pore carriers is similar, but the catalytic performance of porous catalyst carriers with linear gradient porosity distribution is improved by about 10%. This gradient porosity distribution strategy is relatively successful and gives full play to the structural advantages of TPMS.

[0114] The STL geometry file of the methanol reforming hydrogen production variable porosity porous catalyst carrier was imported into the 3D printing post-processing software, and the SLM technology was used for printing. After cleaning the internal powder, the variable porosity porous catalyst carrier was obtained. The SLM printer laser power is 300W, the scanning speed is 1300mm / s, and the printing material used is AlSi10Mg powder, and the powder particle diameter range is 15-53μm.

[0115] Example 3

[0116] Based on the inspiration of the design and performance of the linear variable porosity porous catalyst carrier in Example 2, Example 3 further adopts the mathematical expression of the preferred three-periodic minimal surface based on the present invention, and uses MATLAB mathematical software to generate a nonlinear variable porosity catalytic carrier with a unit cell size of 2×2×2mm and an overall size of 8×8×2mm.

[0117] like Figure 6 As shown, the nonlinear variable porosity porous catalyst carrier is realized by optimizing the equivalent parameter C of the three-periodic minimal surface. In this embodiment, the porosity ε x,y Nonlinear distribution along the x and y axes:

[0118]

[0119] where ε x,y is the porosity of the porous three-periodic minimum unit cell at the coordinate (x, y), b is the porosity change rate of the nonlinear change scheme, ε x,y＝0 is the porosity of the porous three-periodic minimum unit cell at the coordinate origin.

[0120] C=g(ε x,y )

[0121] C=h(x,y)

[0122] According to the fitting relationship between the equivalent parameter C of the three-periodic minimal surface and the unit cell porosity ε, the variation law of the characteristic parameter C of the variable porosity porous carrier with the (x, y) coordinates is obtained, and the nonlinear variable porosity porous catalyst carrier STL geometry file is generated by combining the MATLAB mathematical software algorithm. The porous catalyst carrier synthesized by 3D printing technology can be used in the reactor with the central inlet, and its catalytic performance is significantly better than that of the porous catalyst carrier with uniform porosity distribution.

[0123] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier, characterized in that: The steps include: S1. Modeling of uniform porous catalyst supports with different porosities; S2. Determine the porosity distribution scheme of the porous catalyst carrier with variable porosity by analyzing the finite element model of the flow field of the catalyst carrier with three-period minimal surface of uniform porosity; The S2 comprises the following steps: Establish a finite element model of the flow field of a porous catalyst carrier with three-periodic minimal surfaces of uniform porosity; Calculate and analyze the flow distribution of reactants inside a porous catalyst carrier with three-periodic minimal surfaces of uniform porosity, and obtain the law of reactant flow distribution; Determine the parameterized optimization scheme of variable porosity porous catalyst support according to the flow distribution law of reactants; S3. Use the porosity characteristic parameters of three-periodic minimal curves to perform topology optimization and generate the geometry file of the porous catalyst support with variable porosity; S4. Use multi-physics finite element analysis method to simulate and verify catalytic performance: If the simulation results meet the catalytic performance requirements, proceed to S5; If the simulation result does not meet the catalytic performance requirements, return to S2; S5. Generate a solid porous catalyst carrier using 3D printing technology based on the variable porosity porous catalyst carrier geometry file.

2. The method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier according to claim 1, characterized in that: S1 Modeling of uniform porous catalyst supports with different porosities includes the following steps: Through the unified implicit function of the three-periodic minimal surface, the isosurface function expression φ of the three-periodic minimal surface is generated. (x,y,z) =C, C is the equivalent parameter, C∈[-1,1], and porous structure models with different porosities are obtained according to different C; The shell structure and rib column structure with a certain thickness are constructed by using the equivalent parameter C; The equivalent function parameter C is optimized to generate a variable porosity porous catalyst support model.

3. The method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier according to claim 2, characterized in that: The three-periodic minimal surfaces include: G surface, IWP surface, P surface and S surface.

4. The method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier according to claim 2, characterized in that: The shell structure is generated by defining a closed area surrounded by two different equivalent minimal surfaces with the same period and frequency; the rib column structure is generated by defining the relationship between the equivalent function of the three-dimensional space and the equivalent function value of the minimal surface.

5. The method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier according to claim 4, characterized in that: The shell structure and the rib column structure satisfy the following relationship: -C≤φ sheet ≤C,C≠0 f solid <C,φ volume >C where φ sheet ,φ solid ,φ volume These represent the equivalent function values ​​corresponding to the shell structure, rib column structure and vacuum area respectively.

6. The method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier according to claim 1, characterized in that: The reactant flow distribution law includes: a distribution law in a parallel flow direction and a distribution law in a perpendicular flow direction in a porous catalyst carrier.

7. The method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier according to claim 1, characterized in that: The multi-physics finite element analysis method used in S4 is: Based on the porosity distribution scheme of the variable porosity porous catalyst carrier described in S2, the catalytic performance is analyzed by applying specific boundary conditions using multi-physics field finite element numerical simulation.

8. The method for establishing a variable porosity three-periodic minimal surface porous catalyst carrier according to claim 1, characterized in that: The 3D printing technology includes: fused deposition, selective laser sintering, selective laser melting and stereoscopic printing.

9. A variable porosity three-periodic minimal surface porous catalyst carrier, characterized in that: Acquired by the establishment method described in any one of claims 1-8.

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